Field of the Invention
The present invention relates to an image processing apparatus capable of performing smoothing processing on a drawing object that is obtained by analyzing PDL data described in a page description language (PDL), and a storage medium.
Description of the Related Art
Conventionally, a method for reducing jaggies that occur in the drawing processing of a character or graphics by smoothing processing has been proposed. Jaggies refer to ruggedness that occurs at an edge portion of a character or graphics and there is a tendency for jaggies to appear remarkably in a character or graphics for which monochrome drawing at a high density is specified. FIG. 11A shows an example of jaggies resulting from image processing and FIG. 11B shows an example in which jaggies have been reduced by the smoothing processing. As shown in FIG. 11A and FIG. 11B, by performing the smoothing processing, jaggies are reduced and the edge portion becomes smooth.
In the conventional image processing, whether or not to perform smoothing processing is determined according to the kind (attribute) of a drawing object that is obtained by analyzing PDL data. Further, there is a technique to control whether or not to perform smoothing processing based on the results of comparison by detecting an edge portion of a drawing object and comparing the edge portion with an arbitrary parameter (density value or luminance value) for each pixel constituting the edge portion. Furthermore, there is a method for changing whether or not to perform smoothing processing for each density of a pixel based on the above-described technique (see Japanese Patent Laid-Open No. 2005-129995).
However, with the conventional technique, in the case where the image processing is performed on a drawing object in which there is a difference in density value depending on the drawing position within the same drawing object, such as a drawing object shown in FIG. 4A, there is a possibility that the smoothing processing will switch between ON and OFF within the same drawing object. Due to this, there is such a problem that a density gap greater than supposed occurs within the same drawing object as shown in FIG. 4B.